If uncorrected, astigmatism can sometimes cause distortions in your vision as shown in this photograph. Once the astigmatism is corrected, the streak effect of the lights will dissipate.
If the structures in the eye are spherical (round), then all the light rays that travel into the back of the eye (retina) will form a single point.
For those people who aren't blessed with a perfectly round eyeball, the light rays that come into the eye will focus at two different points.
When both groups of light rays focus in front of the retina, you will have Myopia and Astigmatism. Your prescription might look something like: -X.XX - Y.YY x ZZZ
When one group of light rays focus in front of the retina and the other group focuses somewhere behind it, then you have Hyperopia and Astigmatism. In a case like this, your prescription will look like: +X.XX - Y.YY x ZZZ. Notice, the only thing different here is the plus sign on the first number.
WHAT CAUSES ASTIGMATISM?
If you make an appointment for an eye exam with us, we will be able to determine if you have Astigmatism or not. We will also able to sometimes figure out which structures of the eyes are causing it. Sometimes it's the Cornea which is not round, sometimes it's the Lens, and often it can be a combination of both structures which are not round. Why? We don't always know, but here are some theories below:
Eyelid tension. If the eyelids are more tense (as opposed to floppy), this could steepen the vertical meridian of the cornea causing Astigmatism.
Distance from top lid to the bottom lid can influence it too. People with narrower openings will often have higher amounts of Astigmatism.
After 40, there is a shift towards higher amounts of Astigmatism. This might actually be from lower amounts of eyelid tension, or lens changes like Cataracts.
Chalazias, Hordeolums or Styes can press up on the cornea and also cause Astigmatism.
One other factor proposed is the effect of the extra ocular muscles. When a person converges their eyes, the extra ocular muscles contract and may push the sides of the eyes inward, thus causing a slight warp shape to the eyeball.
ETHNICITY AND ASTIGMATISM
American Native populations have the highest incidence of Astigmatism but the reason for this has not been discovered.
TREATMENT OF ASTIGMATISM
Treatment of is usually geared towards counteracting the optical effects of both sets of light rays focusing in two points of the eye. Lenses (eyeglasses or contact lenses) with a specific cylinder shape are used to bend the light rays so they all focus on the same point: the Retina.